I feel like exploding

70% is still a good score and I'm proud you were able to achieve that. In the UK that would be a grade A! Remember to focus on what you got right and tell yourself I know these areas and I now need to focus on the last 30%.

Also worth saying 10 years after you finish school the grades will count a lot less as people will look at what skills and work experience you have. I'm sometimes involved on the recruitment side and it is more 'is this the right person for the role' than what grade did they achieve 10 years ago.

At the end of the day do the best you can do. That is all anyone can ask.

In terms of stress and life is there any hobbies or interests that you like to do. It's really important to have a balance and ways to unwind.

Anyway I hope things improve for you.

I know this feeling so well. I had that all during my entire youth. My brother used to get praised all the time, while I was just ignored. Noone cared about me and my feelings. I bite on my teeth years and years. But finally my time came, when I became independent , and I got all what I was longing for years and years: Success, admiration, people seeking to be near to me, friends, girls ( earlier I could hardly believe a girl would care a little bit about me), super job, travelling all over the world, children, grandchildren.
Your time will come

You got like 8 to 10 more years , persevere.

And move out and be your own man.

Also remember you don't anyone's approval to be happy.

i know it's not much help, but i'm really sorry to hear your story and hope things work out for you.